In stringed instruments, particularly in the electric guitar, strings vibration is limited within the area between the bridge and the nut, respectively and/or the top lock unit. The bridge is located in the rear portion of the body and is used for locking strings on the body side. The most spread types of guitar bridges are the fixed bridge and the tremolo. Tremolo devices themselves are usually divided into non-locking tremolo and double locking tremolo.
The standard (non-locking) tremolo devices known from the art allow locking of one end of strings, adjusting the strings height thus allowing perfect intonation adjustment and smooth decrease with several tones of a tone being played. On the other side, the utilization of the standard tremolo device results in strings coming quickly out of tune, this type of devices featuring also difficulty in tuning and strings coming out of tune in case of breaking of one of them. Also with existing musical instruments equipped with the standard tremolo device (Non-Locking Tremolo), it is impossible to replace it with double locking tremolo without additional complicated and precise operations such as drilling, milling and painting of the guitar body and neck, the result not always being satisfactory.
The known double locking tremolo devices ensure locking of both ends of each string and allow performing of all the main functions of the non-locking tremolo, avoiding the problems with strings coming out of tune. In addition, the double-locking tremolo devices allow fine tuning after strings are already locked and smooth increase in pitch of a tone being played with several half-tones. On the other side, this type of tremolo device also features difficulties in tuning as with pulling of one string the remaining strings get loosened and the process of tuning of all strings is repeated several times to achieve a good result. The known double-locked tremolo devices have complicated construction with many components, this resulting in significant higher price of the unit and more difficult maintenance. In view of this, it is difficult to adapt and mount the known double-locking tremolo devices on existing instruments, equipped with non-locking tremolo or fixed bridge as complicated manipulation is required for drilling and painting the guitar body and neck.
From U.S. Pat. No. 7,235,730, published on 26 Jun. 2007, possessed by Hoshino Gakki Co. Ltd, Japan and inventor—Shinjiro Hirayama “A Tremolo Bridge for Stringed Instrument and Stringed Instrument” /1/ is known. According to the description to the patent, the tremolo bridge, hereinafter the tremolo device, is intended for stringed instrument, in particular an electric guitar with double string locking. The guitar includes a body, neck with strings and headstock, on the back portion of which the machine heads are mounted. In the body area a tremolo device and adapters for the electronic part are mounted, and at the neck end a top lock unit is provided.
The tremolo device includes a base plate on the upper surface of which a set of saddle assemblies are mounted, corresponding to the number of the instrument strings. Each saddle assembly is formed by lever arm retainer and lever arm, pivotally supported by support shaft, located perpendicularly to the corresponding string and allowing rotation of the lever arm with respect to the lever arm retainer. The base plate is mounted to the instrument body by means of hinge mechanism. String fine tuning devices are provided to the base plate as well as a mechanism for tremolo device manipulation, including a tremolo arm. To the base plate lower side a sustain block is mounted, at the lower end of which a tension applying mechanism is provided with springs mounted also to the lower side of the instrument body.
Each saddle assembly is mounted independently to the base plate and is located along the strings direction. For each saddle assembly cylindrical surface of lever arm is shaped as receiver of the respective string. Each string is fixed in the lever arm of the saddle assembly by cubical clamping block and string fixing bolt provided in a housing formed to this purpose in the lever arm. A spring is provided between the lever arm and lever arm retainer housed in a housing formed in the middle portion of the lever arm. Each lever arm retainer is movably mounted to the base plate as in its front portion a slot is formed in which a bolt is provided and which bolt is statically screwed up in a threaded bore formed in the base plate thus providing for locking of the corresponding saddle assembly to the base plate after intonation adjustment.
The hinge mechanism for fixing the base plate to the instrument body includes a pair of brackets disposed at base plate both ends crosswise to the strings direction and a pair of rotary shafts. Each rotary shaft is supported by both ends of one of the brackets. On left and right sides of the base plate two bearing devices are formed, each one housing a bearing, so that the base plate pivots with respect to the body via the corresponding rotary shaft.
The string fine tuning device includes fine tuning screws and a D tuner device.
For strings fine tuning, fine tuning screws are provided for each saddle assembly of the tremolo device for each one of the five strings. Each screw has a threaded part, smooth part and a head, the threaded part being screwed up statically in the cylindrical bush provided at the base plate back side. The screw smooth part passes through the respective slot of the lever arm from the saddle assembly. In this position the lever arm back end contacts with the screw in a contact surface formed at the lower side of its head, wherein each lever arm is tightened around the corresponding support shaft by means of string tension.
A D tuner device is provided on the base plate at the saddle assembly for the sixth string instead of the fine tuning screw. The device includes cylindrical tuner body and base screw housed in the cylindrical body and is screwed up in a threaded bore provided in the base plate. In the cylindrical tuner body two pairs of engaging recesses and two pairs of inserting recesses are formed at different depth which are perpendicular to each other and which are formed with rectangular cross section with respect to the central hole through which the base screw passes in which adjustment screw is provided screwed up in the base screw by which the tuner tuning of the sixth string is performed.
The tremolo bridge manipulating mechanism includes a threaded cylinder provided at the side base plate portion and directed downwards, wherein the cylinder is mounted to the base plate by means of a nut which is screwed to its lower end on the lower side of the base plate. The tremolo arm is mounted in the cylinder. During tremolo arm manipulation—pulling upwards or pressing the arm Downwards—a slight rotation of the base plate is realized together with the set of saddle assemblies and the sustain block about the shafts housed in the bearing devices of the hinge mechanism against the force created by the tension applying mechanism mounted to the sustain block.
The tension applying mechanism is intended to return the base plate in a balanced position and is provided in the lower portion of the sustain block mounted to the lower surface of the base plate. The tension applying mechanism is housed in a cavity formed to the purpose at the instrument body back side and includes mainly two pairs of springs—two external between which two internal springs are disposed. The pair of internal springs is mounted in its front end to adjustment member connected to adjustment screw mounted to the vertical support piece of a plate statically fixed in the body cavity. The pair of external springs is mounted such as their front ends are fixed to a couple of engaging pins provided in the plate statically fixed in the body cavity. The external springs back ends are fixed to a support rod which is disposed in the back portion of the sustain block, perpendicularly to the neck. The support rod is disposed between V-shaped engaging portions formed in the base. Thus, the V-shaped engaging portions, the pair of external and internal springs, the support rod, adjustment member and screw form the tension applying mechanism to maintain the sustain block and base plate balancing state and bring them back in balanced position.
The tremolo device for stringed instrument according to /1/ possesses the same characteristics as the above described known double locking tremolo devices and provides for slight or almost no strings coming out of tune in case of more serious operation of the device and also opportunity for quick and precise fine tuning.
On the other side in the tremolo device according to /1/ all the above mentioned difficulties in tuning and problems are met that are typical of instruments with double locking tremolo device. In addition, the tremolo device known from /1/:                has a complex construction with many components which leads to significant raising of the instrument cost and to its more difficult maintenance;        in order to use standard strings, their ends (ball strings) have to be cut off in advance;        has smaller sustain block resulting in quicker sound attenuation and a sound poorer in harmony;        it is difficult to adapt and mount it on another type of existing instruments with standard tremolo device or fixed bridge, as the fine tuning screws are moved rather backwards and project beyond the device contour, this leading to complicated milling operations for drilling the guitar body, besides that, when being utilized and the musician's palm being laid upon the tremolo device, it touches the fine tuning screws which leads to additional coming out of tune of the instrument.        
According to /1/, the top lock unit provided at the end of the stringed instrument Neck—the electric guitar—combines the functions of the top lock unit and the intonation nut providing for strings locking at the neck.
From the art is known also a “Locking Nut Assembly for Musical Stringed Instruments”, disclosed in U.S. Pat. No. 5,932,822, published on Mar. 8, 1999, possessed and invented by St. Bernstein /2/. The locking nut assembly is mounted at the end of neck in the area of instrument headstock between the intonation nut and the machine heads.
The known solution /2/ includes a clamping block with tab member mounted by screws to the instrument headstock and formed as integral part of upper wall, lower walls, side longitudinally opposite walls, end cross walls and two internal partial walls which form three internal passageways. To the clamping block, within the formed internal passageways are mounted three countersunk cone-headed screws on both sides of which one string of the instrument is disposed. Within the formed internal passageways on the base plate are provided freely disposed tab members in which the ends of the countersunk head screws are screwed up, to the face of which a tool receiving slot is formed. On the clamping block a locking and releasing mechanism is disposed, including a cylindrical body housing a spindle with a spring, the face spindle surface having a tip—a machine head with identical to the tool receiving slot shape, provided to the end of each screw. At the upper spindle end a rotating lever is provided by means of which the locking and releasing mechanism is shifted along the upper wall of the clamping block. After positioning the mechanism above the screw head, the spindle is engaged to the tool receiving slot in the screw head and is rotated by pressing the respective tab member to the fixing clamping block lower wall, thus locking the respective strings.
The known according to /2/ locking assembly has rather complicated form and a set of components making it cumbersome to operate. In addition, in the known locking assembly:                the provided locking and releasing mechanism on the fixing base plate is unnecessarily complicated as the strings releasing and locking is used only and solely with strings replacement;        the cone-headed screws do not provide even distribution of the compression force on the pair of strings as the strings of the two sides of each screw are with different thickness, i.e., when locking, the thinner string remains unlocked or loosely locked;        the fixing of the locking and releasing mechanism to the guitar headstock results in a rather complex shape body and utilization of greater number of and more complicated components.        